Mechanism of hERG K+ channel blockade by the fluoroquinolone antibiotic moxifloxacin
Mechanism of hERG K+ channel blockade by the fluoroquinolone antibiotic moxifloxacin
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DOI：
10.1038/sj.bjp.0706678
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发表时间：
2006-04-01
影响因子：
7.3
通讯作者：
Leaney, Joanne L.
中科院分区：
文献类型：
--
作者：
Alexandrou, Ari J.;Duncan, Rona S.;Leaney, Joanne L.
1氟喹诺酮类抗生素利多卡因与获得性长QT综合征相关，并在新药QT间期延长潜力的评价中用作阳性对照。与其他QT延长剂一样，已知利福沙星可抑制hERG钾K+通道，但目前关于该作用的机制信息很少。本研究的目的是为了验证阿氟沙星对hERG电流（I-hERG）的抑制作用，并确定S6芳香族氨基酸残基Tyr 652和Phe 656在药物结合中的作用。2使用全细胞膜片钳研究hERG电流在稳定表达hERG通道的HEK 293细胞系中（在室温和在35-37 ° C下）。3莫西沙星以剂量依赖性方式可逆地抑制电流。我们研究了不同电压指令引发hERG电流对利福沙星效价的影响。使用“阶梯-斜坡”方案，IC 50在室温下为65 μ M，在35 ℃下为29 μ M。当使用心室动作电位波形来诱发电流时，IC 50为114 μ M。4发现阿托沙星对hERG的阻断是电压依赖性的，5将S6螺旋残基Phe 656突变为Ala不能消除或减少利福沙星-Tyr 652突变为Ala使利福沙星的阻断作用降低了66%。6我们的数据表明利福沙星阻断hERG通道，优先阻断激活的通道状态。Tyr 652而非Phe 656 S6残基参与了hERG的利福沙星阻断，这与通道内腔中的相互作用一致。
1 The fluoroquinolone antibiotic moxifloxacin has been associated with the acquired long QT syndrome and is used as a positive control in the evaluation of the QT-interval prolonging potential of new drugs. In common with other QT-prolonging agents, moxifloxacin is known to inhibit the hERG potassium K+ channel, but at present there is little mechanistic information available on this action. This study was conducted in order to characterise the inhibition of hERG current (I-hERG) by moxifloxacin, and to determine the role in drug binding of the S6 aromatic amino-acid residues Tyr652 and Phe656.2 hERG currents were studied using whole-cell patch clamp (at room temperature and at 35-37 degrees C) in an HEK293 cell line stably expressing hERG channels.3 Moxifloxacin reversibly inhibited currents in a dose-dependent manner. We investigated the effects of different voltage commands to elicit hERG currents on moxifloxacin potency. Using a 'step-ramp' protocol, the IC50 was 65 mu M at room temperature and 29 mu M at 35 degrees C. When a ventricular action potential waveform was used to elicit currents, the IC50 was 114 mu M.4 Block of hERG by moxifloxacin was found to be voltage-dependent, occurred rapidly and was independent of stimulation frequency.5 Mutagenesis of the S6 helix residue Phe656 to Ala failed to eliminate or reduce the moxifloxacin-mediated block whereas mutation of Tyr652 to Ala reduced moxifloxacin block by similar to 66%.6 Our data demonstrate that moxifloxacin blocks the hERG channel with a preference for the activated channel state. The Tyr652 but not Phe656 S6 residue is involved in moxifloxacin block of hERG, concordant with an interaction in the channel inner cavity.